1. Field of the Invention
The present invention relates to a transformer, and more particularly to an embedded transformer.
2. Description of the Prior Art
A conventional transformer bobbin 10, as shown in FIG. 1, is composed of a bobbin 10 and cores 20, 30. The tubular body of the bobbin 10 is used to accommodate the central posts 25 of the cores 20, 30 and providing winding of wire formed thereon. The wire includes the wire of primary side (not shown) and the wire of secondary side 60, thereafter called wire 60 for short. A plurality of partition walls 50 are formed on the surface of the bobbin 10 so as to isolate the primary side, the secondary side and a plurality of winding grooves located on the secondary side. Each of the partition walls 50 further has a notch 51 formed thereon.
Still referring to FIG. 1, the secondary side of the bobbin 10 further has two pins, including a start terminal 70a and an ending terminal 70b. Among these, the start terminal 70a is used as a terminal from which winding of wire 60 is started and the ending terminal 70b is used as a terminal at which winding of wire 60 is terminated. During the wire 60 extends from the start terminal 70a to the ending terminal 70b, the wire 60 passes the winding groove so as to form windings. Once the winding number of a winding groove conforms to a predetermined value, the wire 60 extends to the next adjacent winding groove, through the above-mentioned notch 51, to form another winding. However, for the simplification of drawing, the present invention merely depicts the wire 60 adjacent to the start terminal 70a and the ending terminal 70b. Unfortunately, during the wire 60 passes the notch 51, the notch 51 is liable to scrape the insulating coating formed on the wire 60 and result in a short circuit.
In sum, the complex bobbin is required for the conventional transformer. Besides, during the wire passes the notch, the insulating coating formed on the wire may be scraped off and result in a short circuit. Accordingly, there has been a strong felt need for a novel transformer for solving the above-mention problems.
Therefore, the main object of the present invention is to provide a novel transformer can overcome aforementioned problems.
Another object of the present invention is to provide a novel transformer can fully take advantage of the resource of the user.
The advantages of the present invention are described as follows. Because the present transformer is embedded in the board, the present transformer has a lower profile compared to the conventional transformer. In the present invention, the required bobbin for the conventional trans former can be omitted. Since the bobbin is omitted, the present invention prevents the insulating coating coated on the wire from scraped off during the wire passes through the notch. Short-circuiting is thus avoided. The manufacturing cost is obviously reduced since the present transformer fully takes advantage of the resource of the user.
The above objects of the present invention are achieved by providing an embedded transformer embedded in a board. The embedded transformer includes a board, a first insulating sheet, a preformed coil, a second insulating sheet, a first core and a second core. Among these, the board includes a conductive pattern formed on an upper surface of the board. A part of the conductive pattern serves as a primary coil of the embedded transformer. The board does not only serve as the base of the conductive pattern, but also includes some electrical component and circuit formed on the remaining part. The designer of the board previously forms the conductive pattern. Besides, the conductive pattern can be formed based on the typical process for forming the trace on the printed circuit board.
The first insulating sheet is formed on the conductive pattern. The preformed coil is formed on the first insulating sheet and serves as a secondary coil of the embedded transformer. Besides, the interposed first insulating sheet electrically insulates the preformed coil form the conductive pattern. The preformed coil further includes a second insulating sheet formed thereon. The first core and the second core are formed on the second insulating sheet and the lower surface the board, respectively. Additionally, the first core and the second core are partially embedded in the board so as to be coupled to each other.